Melatonin (MT) is the messenger of the alternating light and dark phases of the 24h solar cycle, acting through receptors in the circadian clock located in the hypothalamus. The hypothesis is that MT resynchronizes the free running sleep rhythm to the 24h day in blind children with disordered sleep rhythm and, secondarily, improves the child's behavior adjustment and reduces parental stress. Blind school age children ages 6-12 years will participate in 4 outpatient phases: (1) medical and ophthalmological assessment to select patients with total blindness due to lesions of the pathways anterior to the hypothalamus; (2) baseline observation for 4 weeks to determine the presence of disturbed sleep rhythm; (3) randomized, masked treatment using placebo, a physiological and supraphysiological dose of synthetic MT, each given for 8 successive weeks; (4) a long-term open MT trial for 10-30 months, using the dose which seemed most effective in the masked phase. Treatment efficacy will be determined by assessing responses of sleep measures, mainly sleep onset latency, duration of sleep and number of nocturnal wakenings. One subject has been enrolled in the study, and is presently in the third 8-week treatment period. There has been a substantial improvement in the child's sleep rhythm during the treatment phases.